Power control of TAMR element during read/write transition

Abstract

A slider mounted TAMR (Thermal Assisted Magnetic Recording), DFH (Dynamic Flying Height) type read / write head using optical-laser generated surface plasmons in a small antenna to locally heat a magnetic medium, uses the same optical laser at low power to pre-heat the antenna. Maintaining the antenna at this pre-heated temperature, approximately 50% of its highest temperature during write operations, allows the DFH mechanism sufficient time to compensate for the thermal protrusion of the antenna at that lower temperature, so that thermal protrusion transients are significantly reduced when a writing operation occurs and full laser power is applied. The time constant for antenna protrusion is less than the time constant for DFH fly height compensation, so, without pre-heating, the thermal protrusion of the antenna due to absorption of optical radiation cannot be compensated by the DFH effect.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThis invention relates to the fabrication of magnetic read / write heads that employ dynamic fly height (DFH) to control their aerodynamics and TAMR (thermally assisted magnetic recording) to enable writing on magnetic media having high coercivity and high magnetic anisotropy. More particularly, it relates to a method for controlling thermally induced protrusion of a TAMR plasmon antenna to prevent head / disk interference during hard disk drive (HDD) operation.2. Description of the Related ArtMagnetic recording at area data densities of between 1 and 10 Tera-bits per in2 (Tbpsi) involves the development of new magnetic recording mediums, new magnetic recording heads and, most importantly, a new magnetic recording scheme that can delay the onset of the so-called “superparamagnetic” effect. This effect is the thermal instability of the extremely small regions on which information must be recorded, in order to achieve the required data d...

AI Technical Summary

Benefits of technology

It is the first object of this invention to reduce the transient protrusion of a plasmon antenna in a DFH TAMR read / write head caused by differences between the DFH response time and the rate of antenna protrusion caused by optical radiation absorption heating.

These objects will be achieved by slowly preheating the plasmon antenna to a predetermined temperature of approximately 50% of its final temperature in a time comparable to the reaction time of the compensating DFH mechanism. Preferably, this preheating is accomplished using the same laser that produces the final TAMR effect, except the laser will be operated at a lower power. In this way the plasmon antenna will have an already DFH-compensated pre-existing protrusion and the rate of additional protrusion caused by optical heating at full laser power during write operations will now be reduced to the point where it can be adequately compensated by the DFH mechanism. Thus, a protrusion transient will not occur and the read / write head can switch between read and write operations without the danger of head / disk interference.

The fact that preheating places the plasmon antenna at a higher temperature just prior to writing will not adversely affect (e.g. enlarge) the size of the area on the disk surface to which the antenna transfers thermal energy during plasmon activation. Thus, there will be no unwanted erasures of already written data. This is because of the very small time during which the laser activated plasmon near-field area is active as the antenna passes over the disk surface. In fact, the total accumulated time of spot pre-heating of a 50 nm spot on a disk surface due to plasma antenna pre-heating, during a 5 year writing time span is less than 2 minutes.

Problems solved by technology

Satisfying these requirements simultaneously may be a limiting factor in the further development of the present magnetic recording scheme used in state of the art hard-disk-drives (HDD).

If that is the case, further increases in recording area density may not be achievable within those schemes.

The combination of TAMR technology and DFH technology produces the following problem.

However, the time constant for plasma antenna protrusion, ΘPA, is less by a factor between 10 and 50 than the time constant for DFH response, ΘDFH, so the DFH mechanism cannot adequately compensate for the antenna protrusion.

This large difference in response times leads to an antenna protrusion transient during switching between the read / write and write / read condition which can lead to head / disk interference.

None of the above prior art inventions discuss the protrusion transient problem or suggest methods of eliminating it.

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